1. Field of the Invention
This invention relates to a control for a wave compression supercharger and more particularly to such a control that adjusts the position of the engine exhaust gas inlet and outlet ports with respect to the ambient and compressed air inlet and outlet ports.
2. Description of the Prior Art
A wave compression supercharger is essentially a device for producing an exchange of pressure between the high energy state of the exhaust gas of an internal combustion engine and air at atmospheric pressure wherein the air is compressed in the supercharger and delivered to the intake manifold of the engine.
A conventional wave compression supercharger comprises a cylindrical rotor having radially-extending, straight-sided vanes extending from its outer surface enclosed in an outer cylindrical housing. Stationary port plates positioned at opposite ends of the rotor have openings formed through their thicknesses to allow exhaust gas and ambient air to flow into the rotor and the expanded exhaust gas and compressed air to flow from the rotor. The pressure exchange takes place within the rotor cells defined by the spaces on the outer surface of the rotor between adjacent vanes. The process for compressing the ambient air begins when a cell rotates into alignment with the air inlet port, thereby allowing ambient air to flow into the cell. The rotor than brings the cell into alignment with the high pressure exhaust gas inlet port at which time a compression wave enters the cell and begins to travel along the rotor length in the direction of the air port plates. This compression or shock wave travels ahead of the high pressure engine exhaust gas and operates to compress the air in the rotor cell as it travels axially toward the air port plate. The rotor will have rotated out of alignment with the air inlet port by the time the compression wave has begun to travel axially down the rotor.
For efficient operation, it is necessary that the compression wave reaches the air-side end of the cell precisely as the cell rotates out of alignment with the high pressure air exhaust port. This port must be sized and positioned carefully so that the rotor brings the cell to the port when the air in the cell has been compressed to a sufficient pressure but before the engine exhaust gas, located behind the compression wave, reaches the end of the cell and before it can exit the rotor through the port.
In a similar way the engine exhaust gas is purged from the rotor cell after the pressure wave rebounds from the air port plate surface. The rotor cell must rotate into alignment with the exhaust gas outlet port when the compression wave approaches the gas port plate; concurrently, at the air side of the rotor, the cell must be opened to ambient air during a portion of the return of the compression wave to the gas side so that a partial vacuum tending to resist movement of the returning compression wave is not produced.
In view of the timed sequence of events within a wave compression supercharger with respect to the rotor speed, the position and location of the gas and air inlet and outlet ports and of the progression and recession of the pressure wave along the rotor length, it can be appreciated that the device will operate efficiently generally at one speed only. However, the engine of the vehicle that drives the rotor must operate over a wide range of speed. It is, therefore, desirable to expand the efficient operating range of the supercharger to a greater portion of the speed range of the engine.
Wave compression superchargers have heretofore had the exhaust gas and air port plates fixedly mounted in relation to the rotor. The various design parameters relating to the size and location of the ports and length of the rotor are chosen to produce an optimum performance at a single engine speed. The most efficient operation of conventional superchargers, consequently, occurs at the engine speed for which the design parameters are compatible; but efficiency is markedly reduced at engine speeds greater and less than that value.